Factors Influencing Speed in Soap Box Derby Cars

 Over the years I have found the items in the following list to be an influence in the speed and resulting ability of a car and driver to win in soap box derby races. Consider each point as you build your car for your trip down Akron hill.

The photo is a picture taken during a heat of the Central Florida Annual Soap Box Derby race. This is one of the finer tracks dedicated by the City of Sanford Florida to soap box racing.

1. Wheels
2. Axles (Spindles)
3. Weight (Maximum)
4. Weight Distribution
5. Weight Concentration
6. Alignment
7. Axle Mounting
8. Suspension System
9. Axle Trees
10. Length of car
11. Wheel Base (Location of Axles)
12. Center of Gravity
13. Aerodynamics
14. Lubricant
15. Materials (Type of wood, rubber, metal, etc)
16. Vibration
17. Heat
18. Steering System
19. Driving
20. Wind (Direction vs shape of car)

OK now apply the above to the following:


Kinetic Energy = Potential Energy + Waste Energy
     The key is to minimize the waste.
         1. Potential Energy - this is the energy available when the car is sitting at the
             top of the ramp.
         2. Kinetic Energy - this is the moving energy of the car ex: 200# @ 25mph
         3. Wasted Energy - this is from various causes
               A. Bearing friction
                      Crossbind if you put a scale under each front wheel they should read 
                      the same. If they don't the heaviest wheel will have more friction and
                      eat energy.
               B. Tire friction (Toe-in or out) Alignment - the tires use less energy 
                    if they're aligned to go straight no toe-in or out.
               C. Air Friction (sitting up or down)
               D. Suspension Energy - as the car goes down the hill Too springy and 
                    it will eat up your Potential Energy bouncing the car Too Stiff and it 
                    will take more energy to climb over the inconsistencies in the track
         5. Driving Drive the steepest part of the track first.
               Straight down the middle is probably not the fastest way.
               Drive the smoothest part of the track
               Rough areas start the car bouncing, Lightly guide the car with touches 
              of the wheel Don't jerk the wheel to steer guide the car in arcs not corners.
        6. Weight
              Acheive the maximum allowed.
                  The lower the center of gravity the less tenancy for the car to rock from 
                  side to side wasting energy Barbell weights are not a good idea.
         (Note: Don't put all your weight in the center of 
         the car. It'll bounce easier.)

Copyright ; 1998 TL Consulting Group - ALL RIGHTS RESERVED